Pope Francis warns of 'point of no return' on climate change as key Vatican summit begins

Pope Francis shamed and challenged world leaders on Wednesday to commit to binding targets to slow climate change before it's too late, warning that God's increasingly warming creation is fast reaching a "point of no return."

In an update to his landmark 2015 encyclical on the environment, Francis heightened the alarm about the "irreversible" harm to people and planet already underway and lamented that once again, the world's poor and most vulnerable are paying the highest price.

"We are now unable to halt the enormous damage we have caused. We barely have time to prevent even more tragic damage," Francis warned.

The document, entitled Praise God,was unusual for a papal exhortation and read more like a UN scientific report. It carried a sharp tone and its footnotes had far more references to UN climate reports, NASA and Francis's own previous encyclicals than Scripture.

It was released on the feast of St. Francis of Assisi, the pontiff's nature-loving namesake, and was aimed at spurring negotiators to commit to binding climate targets at the next round of UN talks in Dubai beginning Nov. 30. It also comes as the Vatican gathers Catholic leaders from around the world to discuss the future of the church in a three-week closed-door meeting, known as a synod.

Human effect on climate undeniable: Francis

Francis took square aim at the United States, noting that per capita emissions in the U.S. are twice as high as in China and seven times greater than the average in poor countries.

While individual, household efforts are helping, "we can state that a broad change in the irresponsible lifestyle connected with the Western model would have a significant long-term impact," he said.

Using precise scientific data, sharp diplomatic arguments and a sprinkling of theological reasoning, Francis delivered a moral imperative for the world to transition away from fossil fuels to clean energy with measures that are "efficient, obligatory and readily monitored."

"What is being asked of us is nothing other than a certain responsibility for the legacy we will leave behind, once we pass from this world," he said.

Francis's 2015 encyclical Praise Be was a watershed moment for the Catholic Church, the first time a pope had used one of his most authoritative teaching documents to recast the climate debate in moral terms.

In that text, which has been cited by presidents, patriarchs and premiers and spurred an activist movement in the church, Francis called for a bold cultural revolution to correct a "structurally perverse" economic system where the rich exploit the poor, turning Earth into an "immense pile of filth."

Even though encyclicals are meant to stand the test of time, Francis said he felt an update to his original was necessary because "our responses have not been adequate, while the world in which we live is collapsing and may be nearing the breaking point."

He excoriated people, including those in the church, who doubt mainstream climate science about heat-trapping greenhouse gas emissions, sarcastically deflating their arguments and showing his impatience with their profit-at-all-cost mentality.And he cited data showing that increased emissions and the corresponding rise in global temperatures have accelerated since the Industrial Revolution, and particularly in the last 50 years.

"It is no longer possible to doubt the human 'anthropic' origin of climate change," he asserted.

Laments lack of progress on Paris goals

While acknowledging that "certain apocalyptic diagnoses" may not be grounded, he said inaction is no longer an option.

"Small changes can cause greater ones, unforeseen and perhaps already irreversible, due to factors of inertia," he noted. "This would end up precipitating a cascade of events having a snowball effect. In such cases, it is always too late, since no intervention will be able to halt a process once begun."

WATCH l Pope says urgent action needed on climate crisis:

Pope warns climate is approaching 'the point of no return'

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In a pastoral letter, Pope Francis is challenging world leaders to commit to binding targets to slow climate change, warning creation is reaching a 'point of no return.' The document was published ahead of a Vatican summit this week and the UN climate talks in November.

In the landmark 2015 Paris Agreement, countries of the world agreed to try to limit warming to 1.5 C or at least 2 C since pre-industrial times. It's already warmed about 1.1 C since the mid-1800s.

Francis said it was clear that the Paris target will be breached and will soon reach 3 C, and that already the effects are obvious, with oceans warming, glaciers melting and the world registering record heat waves and extreme weather events.

"Even if we do not reach this point of no return, it is certain that the consequences would be disastrous and precipitous measures would have to be taken, at enormous cost and with grave and intolerable economic and social effects," he warned.

Since 2015, the world has spewed at least 288 billion metric tonnes of heat-trapping carbon dioxide into the air, not including this year's emissions, according to the scientists at Global Carbon Project.

The record-hot summer of 2023 is one-third of a degree C warmer than the summer of 2015, according to the U.S. National Oceanic and Atmospheric Administration.